Sheets of cardboard mat, glass and other materials are frequently cut to provide components having openings and/or perimeters of rectangular, circular or elliptical (generally referred to as "oval") configuration. Such components are widely used for mounting and framing of pictures and the like.
Machines are known in the art, and are commercially available, for cutting planar workpieces to such shapes; exemplary of machines designed for cutting circles and ovals is the device described in Pierce U.S. Pat. No. 4,112,793, issued Sept. 12, 1978. Although many of the known machines are highly effective for their intended purposes, often they are not optimal in various respects.
For example, in cutting openings in mat board for framing pictures the blade will generally be inclined at a nonperpendicular angle, so as to produce a beveled edge on the mat. Because the incline of the blade is predetermined, cutting must occur either from the front or the rear of the workpiece; i.e., there is usually no choice. Furthermore, it is often desirable to produce a V-shaped groove in the surface of the mat board surrounding the opening cut, and in many instances the means provided for doing so is unsatisfactory, or indeed the cutting head is not at all suited to that purpose.
It is of course necessary in any such machine that the sheet material workpiece be maintained securely in position, so as to promote ultimate accuracy and perfection in the cut produced, and that therefore effective means be provided for clamping the work in place. It is also desirable that the clamping system be as unobtrusive as possible, so as to avoid any possibility of interference with the cutting mechanism; this is particularly important when the mechanism moves widely during operation. As will be appreciated, systems such as that which are shown in the above-cited patent are not optimal in this respect.
Accordingly, it is the broad object of the present invention to provide a novel machine for cutting shapes in planar workpieces, which permits facile and effective clamping and precise positioning of the workpiece, which permits accurate cutting of bevels from either the front or back of the workpiece; and which permits convenient and accurate V-grooving thereof.
A more specific object of the invention is to provide a novel clamping system affording the foregoing benefits, which is, in addition, of relatively uncomplicated design and construction, which does not intrude into the cutting space, and which imposes no load on the cutting mechanisms or on the structure by which it is supported.
Another more specific object is to provide a novel cutting head and head assembly affording the foregoing benefits, which is, in addition, of relatively uncomplicated design and construction, and which is capable of readily disposing either of two blades in an optimal position for effective cutting of the workpiece, and for producing cut edges which may be virtually flawless.